Group equipment and blocks of asynchronous conjugation

Four streams of the previous step of hierarchy are multiplexed into next level digital stream in the European hierarchy. The converter of a reception code (CRCod.) converts the AMI (Alternate Mark Inversion) signal to the binary unipolar code. The return transformation (binary unipolar to AMI) carried out by means of the converter of a transmission code (CTCod). There are two types of block of justification (BJ): the BAJ (the block of asynchronous justification) and BSJ (the block of synchronous justification).

Figure 5.1 – Block diagram of high-order time division multiplexer

Scheme of group equipment consists of:

-GE-generator equipment. This device is used for generating signals with different frequencies.

-MD-multiplexing device. This device is used for signal multiplexing, forms a frame of group signal. It consist of:

-symbols of input digital streams (payload);

-service communication (SC);

-the control and signalling (CS);

-discrete information symbols (DI).

-DD-demultiplexing device. Inverse to MD.

-FAD-the frame alignment device in the transmission path (FADtr) forms a synchronization signal for multiplexing device.

-The group signal from MD output encodes in the CTCod and transmits into a line path. The group signal from line path output is decoded in CRCod. In the reception path the return transformation carry out.

-BJ-block of asynchronous justification.

Asynchronous justification is more difficult (in comparison with synchronous justification) at the realization because the justification of bitrates (fciki ~ fcik4)ls necessary for carrying out.

Figure 5.2 – Sub-circuit of high-order TDM for one digital stream

Multiplexed digital streams have a different clock rate in general case. Therefore in high-order time-division multiplexer these rates are adjusted to a uniform clock rate for all these streams (it is formed in the generation equipment). This process is called justification. It is carried out in the BAJtr.

Figure 5.3 - BAJ of the transmitter

At the transmitter part, input stream is written to the memory device of the synchronous equipment and is read sequential pulses from generator equipment. Process of written is controlled by extracted stream pulses of sequential pulses frequencies. For control of common time position and for reading it is used time discriminator TD.

Figure 5.4 - BAJ of the receiver

In the receiving part the reading is work with frequency which is equal to the pulse’s frequency in the input of the equipment. It is help us to reconstruct the initial frequency of transmission. For compensation of time fluctuations of input digital stream in the memory devices with on additional memory cells: for working with local network - from one to three, for international communication network - to ten cells.

Дата добавления: 2015-08-18